| 1. |
- Aamodt, K., et al.
(författare)
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The ALICE experiment at the CERN LHC
- 2008
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 3:S08002
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Forskningsöversikt (refereegranskat)abstract
- ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries, Its overall dimensions are 16 x 16 x 26 m(3) with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.
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| 2. |
- Joco, V., et al.
(författare)
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Surface phase transition and electronic structure of c(5 root 2 x root 2)R45 degrees-Pb/Cu(100)
- 2006
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Ingår i: Proceedings of the 23th European Conference on Surface Science (Surface Science). - : Elsevier BV. - 0039-6028. ; 600:18, s. 3851-3855
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Konferensbidrag (refereegranskat)abstract
- The c(5 root 2 x root 2)R45 degrees-Pb/Cu(100) surface phase is investigated by means of angle resolved ultraviolet photoemission and low energy electron diffraction in the temperature range between 300 and 550 K. We identify and characterize a temperature-induced surface phase transition at 440 K from the room temperature e(5 root 2 x root 2) R45 degrees phase to a (root 2 x root 2)R45 degrees structure with split superstructure spots. The phase transition is fully reversible and takes place before the two-dimensional melting of the structure at 520 K. The electronic structure of the split (root 2 x root 2)R45 degrees phase is characterized by a metallic free-electron like surface band. This surface band is backfolded with c(5 root 2 x root 2)R45 degrees periodicity phase at room temperature, giving rise to a surface band gap at the Fermi energy. We propose that a gain in electronic energy explains in part the stability of the c(5 root 2 x root 2)R45 degrees phase. (c) 2006 Elsevier B.V. All rights reserved.
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| 3. |
- Martinez-Blanco, J, et al.
(författare)
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Surface phase diagram and temperature induced phase transitions of Sn/Cu(100)
- 2006
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Ingår i: Proceedings of the Eight International Conference on Atomically Controlled Surfaces, Interfaces and Nanostructures and the Thirteenth International Congress on Thin Films - ACSIN8/ICTF13 (Applied Surface Science). - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 252:15, s. 5331-5334
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Konferensbidrag (refereegranskat)abstract
- Room temperature deposition of Sn on Cu(100) gives rise to a rich variety of surface reconstructions in the submonolayer coverage range. In this work, we report a detailed investigation on the phases appearing and their temperature stability range by using low-energy electron diffraction and surface X-ray diffraction. Previously reported reconstructions in the submonolayer range are p(2 x 2) (for 0.2 ML), p(2 x 6) (for 0.33 ML), (3 root 2 x root 2)R45 degrees (for 0.5 ML), and c(4 x 4) (for 0.65 ML). We find a new phase with a ((-4)(0) (2)(4)) structure for a coverage of 0.45 ML. Furthermore, we analyze the temperature stability of all phases. We find that two phases exhibit a temperature induced reversible phase transition: the (3 root 2 x root 2)R45 degrees phase becomes (root 2 x root 2)R45 degrees phase above 360 K, and the new ((-4)(0) (2)(4)) phase becomes p(2 x 2) also above 360 K. The origin of these two-phase transitions is discussed. (c) 2005 Elsevier B.V. All rights reserved.
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